Safety air bag systems for use in automobiles which respectively employ a shock sensor for sensing a shock which will be applied to a vehicle upon collision with the other vehicle or an object are intended to protect a driver from such a shock by starting an actuator for the safety air bag system with an output signal from the sensor which has sensed the collision shock, and inflating the air bag.
FIGS. 1 and 2 respectively show an example of this type of conventional shock sensor.
FIG. 1 shows a shock sensor which utilizes a magnetic repulsion force of magnets.
This example of the conventional shock sensor in FIG. 1 is adapted to employ a main casing 141 having tunnel type chambers 142 and 143, which are provided parallel to each other, to house a reed switch 144 in one tunnel type chamber 142 and a pair of rod type magnets 145 and 146 in the other tunnel type chamber 143 so that the same magnetic poles (S pole in this example) of these magnets are arranged to oppose each other; for example, one rod type magnet 145 is slidably provided and the other rod type magnet 146 is fixed.
This shock sensor is arranged so that the slidable rod type magnet 145 is positioned in a direction opposing to the direction of the shock to be detected.
In this shock sensor, a pair of magnets 145 and 146 are kept at a position shown in FIG. 1, that is, a position away from the contact part 144a of the reed switch 144 by their magnetic repulsion force in a normal state where no shock is applied.
When the shock sensor receives a shock in a direction where the shock sensor expects the shock in this normal state, the rod type magnet 145 slidably provided moves against the magnetic repulsion force produced between the rod type magnet 145 and the fixed rod type magnet 146 to approach the contact part 144a of the reed switch 144 and actuates the reed switch 144 by applying magnetism to this contact part 144a and the shock sensor detects the shock.
FIG. 2 shows a shock sensor which utilizes spring resilience.
This example of the conventional shock sensor in FIG. 2 is provided with a main casing 251 having tunnel type chambers 252 and 253 which are arranged parallel to each other, the tunnel type chamber 252 being adapted to incorporate a reed switch 254 and the tunnel type chamber 253 being adapted to incorporate a rod type magnet 255 to be slidable, and thereby the rod type magnet 255 is energized by the spring 256 to move away from the contact part 254a of the reed switch 254.
In this shock sensor, the magnet 255 is kept at a position shown in FIG. 2, that is, a position away from the contact part 254a of the reed switch 254 by the resilience of the spring 256 in the normal state where no shock is applied.
When a shock is applied to the shock sensor in this normal state in the lengthwise direction of the reed switch 254 where the resilience of the spring 256 is reduced, the magnet 255 moves against the resilience of the spring 256 to approach the contact part 254a of the reed switch 254 whereby the reed switch 254 is actuated by applying the magnetism to the contact part 254a and thus the shock sensor detects a shock.
Any example of conventional shock sensors with the configuration as described above is provided with the magnets which are arranged to be slidable in the lengthwise direction of the reed switch and therefore, there has been a problem that the reed switch operates only with a shock applied to one side of the lengthwise direction of the reed switch and does not operate with a shock applied to the opposite side.
An object of the present invention made in view of the above problem is to provide a shock sensor capable of detecting a shock in a number of directions. Another object of the present invention is to provide a shock sensor capable of allowing to conduct operation tests more easily.